Composition



highly desirable in diesel starter fluids.

United States PatentO COMPOSITION Hobert D. Young, Hammond, Ind., assignor to Sinclair Claims. (Cl. 123-1) My invention relates to a starting fluid for use in compression ignition engines which is particularly valuable in cold weather for low temperature starting. In particular, my invention provides fluids effective at sub-zero temperatures down to about -40 F.

It is well known that compression ignition engines employing regular diesel fuels are difficult to start under conditions of low ambient temperature particularly at temperatures below about 32 F. engine, the temperature within the cylinder must be sufliciently high to ignite the regular fuel. Such temperatures are developed only after 's'uflicient work has been done in compression of the charges within the working cylinder to bring the parts of the engine in direct heat exchange relation with the contents of the working cylinder, as well as the charge undergoing compression, to a relatively high temperature. Thus, at low ambient temperatures it is often diflicult, if not impossible, to attain such required temperatures without special equipment and starting methods.

With the widespread use of diesel engines, particularly in mobile auto-powered equipment in the transportation, construction and military fields, cold weather starting difliculties for such engines often involve serious economic loss above the mere delay in use of the automotive equipment. Delay of starting is, of course, extremely important in military equipment. Hence considerable time and attention have been given to the problem of obtaining reliable and inexpensive positive cold weather start:- ing methods. Such methods employ Winterizing techniques and mechanical starting aids, for example, com bustion type air induction heaters, glow plugs, external heaters-for engine jacket coolants, jacketed crankcases, jacketed battery cases and the like.

In. starting a cold One such method for starting of compression ignition engines contemplates the use of an auxiliary fuel, a starting fluid, in combination with the regular, primary fuel, The auxiliary fluid, for example diethyl ether, is finely aspirated by suitable means into the air intake system of the engine during starting until combustion of the regular injected fuel is continuous.

I have discovered that volatile organic nitrates, par;- ticularly alkyl nitrates, e.g. amyl nitrate, possess specially desirable properties, such as marked ignition response to low temperatures and pressures, when atomized into the heptane, possess additional extremelyuseful properties My invention provides a starting fluid containing about 10 to per cent by volume of the ether, about 10 to 70 percent by volume of the alkyl nitrate and about 10 to 60 percent by volume of the light paratfinic fraction. Compositions of maximum performance effectiveness fall within the approximate range of about 20 to 50 percent by volume of the ether, about 20 to 50-percent by volume of alkyl nitrate and about 20 to 50 percent by volume of the light paraflinic fraction. -I prefer a composition of about 40 percent by volume of diethyl ether, about 20 percent by volume of amyl nitrate and about 40 percent by volume of normal-heptane. I particularly prefer a composition of about 40 percent by volume of diethyl ether, about 40 percent by volume of amyl nitrate and about 20 percent by volume of normal-heptane.

The starting fluids of my invention provide effective cold starting fluids suitable for sub-zero use when properly applied to the intake manifold of an internal combustion engine. In particular, the fluids are eflective at all fluid temperatures down to about 40 F. as com.- pared with only 27 F. for diethyl ether alone. Also, burningof the fluid is smooth and detonation is reduced significantly. Diethyl ether alone produces disadvan} tageous severe detonation. Diethyl ether burns so rapidly when ignited that severe detonation may be produced due to extremely high rate of pressure rise. Due to the rapid rate of heat release, diethyl other may fail to ignite the regular diesel fuel simultaneously injected. The fluids possess a valuable combination of properties which provides a fluid of significantly improved performance characteristics. For example, the fluids have .an equivalent cetane number in excess of and .thus have a correspondingly short ignition delay. They possess a spontaneous ignition temperature of slightly below 380 F. and are highly pressure and temperature sensitive to ignition. Such fluids, therefore, ignite quickly at the low compression pressures and temperatures which prevail at low engine cranking speeds at sub-zero temperatures. The pronounced pre-flame reaction characteristics exhibited by fluids of this type plus their low rate of pressure rise after ignition results in a significant reduction in detonation. The longer burning duration of fluids of this type due to nature of the constituents results in earlier ignition of the regularly injected diesel fuel,'thus engine warm-up-time is reduced. These properties coupled with volatility characteristics suitable for achieving a high degree of atomization where properly applied at low temperatures result in a highly effective type of fluid starting aid. While the blends are sufliciently volatile .for aspiration into the engine intake air by suitable means -to give a finely comminuted fluid/air mixture capable of being drawn into the combustion chambers without drop-out of the fluid particles en route under'severel'y cold weatherconditions, yet such volatilities are 'insuflicient to amount to a hazardous problem in warm weather and consequently the blended fluids can be conveniently stored and handled; These properties are highly desifable foreffective starting fluids. 7

The useful predominantly parafiinic, low pour point, light petroleum fractions are those composed mainly of one or more of the normal paraflins heptane, octane; nonane and decane. Representative constituents of gaso; lines such as aromatics, naphthenes, olefins, iso-partaffins, andthe lower boiling point n-paraffins are un'suite able as cold starting aids. Higher boiling point; mparaffins are unsuitable due to their high freezing points, Preferably, the paraflinic petroleum fraction is normal; heptane. The h-heptane can contain minor amo nntsof other materials such as isomers or close homologues but these'materials preferably should not exceed about percent. Preferably, the n-heptane is'99 percentpure.

The alkyl nitrates useful in my invention are primary and secondary alkyl nitrates containing from 4 to 8 carbon atoms, for example, butyl, amyl, hexyl, heptyl and octyl nitrates. Preferably, amyl nitrate is used. The amyl nitrate can be normal-amyl or iso-amyl or other isomers, for example, 2-methyl-l but-yl nitrate. The l carbon atom ethers whichI- employ include'diethylether, methylrpropyl ether and methyl'isopropyl-ether. 'The fluids of my invention or the primary fuel with which they are used, e.g., diesel fuel, can contain-othercomponents. g

In evaluating the effectiveness of various materials posses-sing potential "merit as starting fluids a useful tool -can be employed. This tool is a variable-compression ratio, single cylinder, turbulent -"chamber-'CFR "engine. It is well known-that the critical compression ratio '(CCR') of adiesel fuel is a reliable measure-ofease o'f'ignition (ignition delay period). "The lower the compression-ratio at which auto-ignition takes place under a 'given set of test and engine operating'conditions ithebetterthe fuel "from the standpoint of'ease 'of ignition. "If the critical compression ratio of a given diesel fuel employed for reference is first established and then apotentially'effec- 'tive starting fluid introduced into'th'e intake air of "the engine, simultaneously 'with injection of the reference diesel fuel and under prescribed conditions, a critical compression ratio lower than that obtained with the reference diesel fuel "should be obtained if the material being "evaluated as a starting fluid possesses'anym'erit'. 'Thus,

the 'magnitude'of' difference between the two critical comfpression ratios,'termed the critical compression'ratio difdu'ced coolingjacket-temperatures and at a speed of -900 *s inglecylin'der CFR diesel with a turbulent combustion chamber.

(fooIanttemperature 1 10' F. Primary fuel injectionrate ld ccsper minute.

7 "To evaluate the starting characteristics and eifectiveness of secondary fuel aspirated with the airintake, the further test conditions were employed:

Primary fuel used SOcetane number die- =sel fuel of 350-675 boiling range.

Quantity secondary fuel aspirated per trial 7"cc. in l0 seconds.

The engine was constantly motored:-atl.9'00r.p.m. under equilibrium conditions except'for 10-secondffuelinjection at each trial. The initial compression ratio for-the engine was set below the point at whichignition of the primary fuel occurred for an injection duration .of 110 seconds. From thisnpoint the compression ratio was gradually raised :at IO-second intervals .until the critical compressionratio 'of the primary fuel 'was reached, as evidenced by continuous combustion of the fuel. When this value was -determined by three separate determina- -t'io1 :'ls,'the"compression ratio was againsubstantially lowcred and the critical ratio of the primary fuel jplus aspirated secondary fuel was determined in like manner.

The difi'erence between the two values represents the *criticalcompressiOnratiodifference (CCRD) of the secondary fuel.

Under these test conditions the CCRD data were determined using as starting fluids diethyl ether, a proven and well known auxiliary starting fluid; amyl nitrate; normal-heptane; blends of diethyl ether and normal-heptane (a starting fluid described in my U.S. Patent 2,575,- 543 issued November 20, 1); and blends of diethyl ether, amyl nitrate and normal h'eptane in various proportions by volume. The following-table illustrates the results:

. :As "illustrated by the above data, surprisingly blends of diethyl ether, amyl nitrate :and normal-heptane exhibited betterperformance characteristicsfor cold weather starting as measured by the CCRD value,-- than are exhibited by either diethyl 'ether, amyl :nitrate-or-normah heptane alone or bycblends-of diethylether and mormalheptane. =It 'is particularly surprising that the blends o'f our invention provide better performance characteristics than diethyl ether since -diethyl etheris one of xth'BE'IIiOSt effective of starting fluids previously known. This -isrbe lieved to b'e-due to the'eflects of the various desirable qualities of our starting fluid, namely, rapi'cl triggering of ignition :of-the .fluid, low rate of pressure rise :after ignition, extended burning of theifluid over a fairly wide range of "engine 1 crank angles, and volatility suitable .for the'sformation fof finely comminuted mixtures with air whenatomizedinto the intake air by suitable-means. It is -.to be noted that as the three-component blends'con- -tain amounts :of normal-heptane approaching :the useful .upper limit "of 60%, the CCRD value approaches that of the two component blends containing similar amounts of heptane.

Moreover the above results show that amyl nitrate is almost as eifective a'secondary fuel asdiethyhether', as it has aCCRD'value "approaching that "for "diethyl ether. However, amyl "nitrate is "not as useful in ex tremely'cold weathersince it has'low volatility. The blends of amyl nitrate, diethyl ether and normal heptane, however, surmount these J difliculties, 1 having the .requisite 10w pourpoint characteristics and volatilityafor atomization with-the air :intake even .under 'severly low temvpnaratures.

{Other tests were :performed to determine ithe time required for starting-engines using a .blend 1 of 40% amyl nitrate-40% diethyl'ether and 20% n-h'epta'ne as astartingffluid. The engines were fullscale.automotive die'sel engines. The tests were 'run in a laboratory "cold'room."

The engines, 'batteriesand staiting fiuid' were cold Soaked at fthetesttemperatur'e foragp'eriod of 24 hours priorto making a' 'starting trial. The "primaryfuel'usd Tcorrespon'ded Ito winter grade diesel mayor-11 i speeified under Federal specification VV-F-800, December 17, 1954. Its characteristics were as follows:

The lubricating oil corresponded to MIL-O-l0295. The starting fluid was injected into an intake manifold at the point of maximum air flow velocity. The time required to fire and sustain combustion until the engine can operate on regular diesel fuel was measured and is listed under second to start in Table H below. The engines failed to start at the temperatures listed in Table II when no starting fluid was used.

Table II ENGINE: GM3-71, 3 CYLINDER Fluid Min. Oranking Used, Seconds Run Temp., Speed, cc. to to Start F. r.p.m. Start and Run and Run ENGINE: BUDA, MODEL 1BD38, SINGLE CYLINDER ENGINE: 1110, MODEL (ID-14A, 4 CYLINDER The above results show the effectiveness of the starting fluid in starting diesel engines at sub-zero temperatures. The manner in which starting fluids are best used is known to the art. For details and diflerent suggested methods of aspiration I make reference to my US. Letters Patent No. 2,575,543, issued November 20, 1951.

I claim:

1. A starting fluid for compression ignition engines consisting essentially of about 10 to 70 percent by volume of an alkyl ether of 4 carbon atoms, about 10 to 70 percent by volume of an alkyl nitrate of from 4 to 8 carbon atoms, and about 10 to percent by volume of a predominantly straight chain paraflinic, low pour point, light close out petroleum fraction boiling Within the approximate range of 200 to 350 F. and containing from 7 to 10 carbon atoms.

2. The fluid of claim 1 in which the alkyl nitrate is amyl nitrate, the alkyl ether is diethyl ether and the paraflinic petroleum fraction is normal-heptane.

3. The fluid of claim 1 in which the percent of alkyl ether is 20 to 50, the percent of alkyl nitrate is 20 to 50, and the percent of paraflinic petroleum fraction is 20 to 50.

4. The fluid of claim 3 in which the alkyl nitrate is amyl nitrate, the alkyl ether is diethyl ether and the parafiinic petroleum fraction is normal-heptane.

5. A starting fluid for compression ignition engines consisting essentially of about 40 percent by volume of diethyl ether, about 20 percent by volume of amyl nitrate and about 40 percent by volume of normal-heptane.

6. In the operation of internal combustion engines of the compression ignition type, the improvement which comprises burning a primary fuel while introducing with the air supply the fluid of claim 1.

7. In the operation of internal combustion engines of the compression ignition type, the improvement which comprises burning a primary fuel while introducing with the air supply the fluid of claim 2.

8. In the operation of internal combustion engines of the compression ignition type, the improvement which comprises burning a primary fuel while introducing with the air supply the fluid of claim 3.

9. In the operation of internal combustion engines of the compression ignition type, the improvement which comprises burning a primary fuel while introducing with the air supply the fluid of claim 4.

10. In the operation of internal combustion engines of the compression ignition type, the improvement which comprises burning a primary fuel while introducing with the air supply the fluid of claim 5.

References Cited in the file of this patent UNITED STATES PATENTS 2,158,050 Bereslavsky May 16, 1939 2,280,217 Cloud Apr. 21, 1942 2,493,284 Farkas Jan. 3, 1950 2,575,543 Young Nov. 20, 1951 2,655,440 Barusch et al Oct. 13, 1953 

1. A STARTISNG FLUID FOR COMPRESSION IGNITION ENGINES CONSISTING ESSENTIALLY OF ABOUT 10 TO 70 PERCENT BY VOLUME OF AN ALKYL ETHER OF 4 CARBON ATOMS, ABOUT 10 TO 70 PERCENT BY VOLUME OF AN ALKYL NITRATE OF FROM 4 TO 8 CARBON ATOMS, AND ABOUT 10 TO 60 PERCENT BY VOLUME OF A PREDOMINANTLY STRAIGHT CHAIN PARAFFINIC, LOW POUR POINT, LIGHT CLOSE CUT PETROLEUM FRACTION BOILING WITHIN THE APPROXIMATE RANGE OF 200 TO 350*F. AND CONTAINING FROM 7 TO 10 CARBON ATOMS. 